* BKL use in ptrace
@ 2009-12-20 18:53 Andi Kleen
2009-12-21 17:02 ` Oleg Nesterov
0 siblings, 1 reply; 3+ messages in thread
From: Andi Kleen @ 2009-12-20 18:53 UTC (permalink / raw)
To: oleg, linux-kernel; +Cc: torvalds
Hi,
ptrace has this comment/BKL use:
/*
* This lock_kernel fixes a subtle race with suid exec
*/
lock_kernel();
But unless I'm blind I don't see execve actually getting the BKL
anywhere. So is this comment outdated or misleading (is the race with exit?)
or is there a bug?
Thanks,
-Andi
--
ak@linux.intel.com -- Speaking for myself only.
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: BKL use in ptrace
2009-12-20 18:53 BKL use in ptrace Andi Kleen
@ 2009-12-21 17:02 ` Oleg Nesterov
2009-12-22 1:13 ` Roland McGrath
0 siblings, 1 reply; 3+ messages in thread
From: Oleg Nesterov @ 2009-12-21 17:02 UTC (permalink / raw)
To: Andi Kleen; +Cc: linux-kernel, torvalds, Roland McGrath
(add Roland)
On 12/20, Andi Kleen wrote:
>
> ptrace has this comment/BKL use:
>
> /*
> * This lock_kernel fixes a subtle race with suid exec
> */
> lock_kernel();
>
> But unless I'm blind I don't see execve actually getting the BKL
> anywhere. So is this comment outdated or misleading (is the race with exit?)
> or is there a bug?
I never understood this lock_kernel().
In any case it looks outdated. We were going to kill it "soon",
along with other ptrace changes.
Oleg.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: BKL use in ptrace
2009-12-21 17:02 ` Oleg Nesterov
@ 2009-12-22 1:13 ` Roland McGrath
0 siblings, 0 replies; 3+ messages in thread
From: Roland McGrath @ 2009-12-22 1:13 UTC (permalink / raw)
To: Oleg Nesterov; +Cc: Andi Kleen, linux-kernel, torvalds
> I never understood this lock_kernel().
>
> In any case it looks outdated. We were going to kill it "soon",
> along with other ptrace changes.
I never understood it either. It's very ancient and long predates many,
many ptrace cleanups. If the comment was ever accurate, then any issue
like that is now covered by cred_guard_mutex. I don't know of any reason
for (or really, effect of) using BKL in ptrace.
Thanks,
Roland
^ permalink raw reply [flat|nested] 3+ messages in thread
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2009-12-20 18:53 BKL use in ptrace Andi Kleen
2009-12-21 17:02 ` Oleg Nesterov
2009-12-22 1:13 ` Roland McGrath
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